Nitrous oxide detection at 5.26 µm with a compound glass antiresonant hollow-core optical fiber.

Laser-based gas sensors utilizing various light-gas interaction phenomena have proved their capacity for detecting different gases. However, achieving reasonable sensitivity, especially in the mid-infrared, is crucial. Improving sensor detectivity usually requires incorporating multipass cells, which increase the light-gas interaction path length at a cost of reduced stability. An unconventional solution comes with the aid of hollow-core fibers. In such a fiber, light is guided inside an air-core which, when filled with the analyte gas can serve as a low-volume and robust absorption cell. Here we report on the use of a borosilicate antiresonant hollow-core fiber for laser-based gas sensing. Due to its unique structure and guidance, this fiber provides low-loss, single-mode transmission $ {\gt} {5};{\unicode{x00B5}{\rm m}}$>5µm. The feasibility of using the fiber as a gas cell was verified by detecting nitrous oxide at 5.26 µm with a minimum detection limit of 20 ppbv.